Introduction

Breast cancer is the most common cancer in North American women, accounting for about a third of all incident cancers. In 2004 in the USA, there are projected to be 215 900 newly diagnosed cases of female breast cancer and 40 110 deaths. During the past 5 years, the mortality rate for breast cancer has declined significantly, most likely due to a combination of wider use of mammographic screening and the diffusion of adjuvant therapy for stage I and II disease. In spite of this improvement in mortality, the number of incident cases of breast cancer is projected to rise with the continued aging of the population, as breast cancer peaks in women in the 8th decade of life.– Unless major advances in the prevention of breast cancer occur, using chemoprevention and other risk reduction strategies, the absolute number of breast cancer patients and survivors will continue to increase as we move further into the 21st century.

The majority of women with breast cancer are diagnosed with early-stage localized disease. In fact, tumor size at diagnosis has continued to decrease, with very small invasive and non-invasive cancers being detected through mammographic screening. Some series estimate that about 20% of incident cases are now non-invasive (stage 0) ductal carcinoma in situ. However, in spite of these decreases in tumor size and invasiveness, almost all patients diagnosed with breast cancer receive localized breast surgery (breast-conserving surgery and radiation to the breast or a modified radical mastectomy, with or without reconstruction).